安裝好mysql數據庫 安裝後檢查是否有connection J 的程序 第一步導入架包，加載驅動程序 發起請求java
第一步的程序 url 若是寫成 jdbc:mysql://localhost:3306/student?useUnicode=true&characterEncoding=utf8 ； 有可能會報錯 ——>java.sql.SQLException: The server time zone value ........ 這時候參考博文：https://blog.csdn.net/Hello_World_QWP/article/details/80421533 也就是用下面個人url 裏 +？......的部分mysql
Class.forName("com.mysql.jdbc.Driver");//通常都是已經加載好的 加入後可能會警告
System.out.println("驅動加載成功");
String url = "jdbc:mysql://localhost:3306/mysql2_1709?serverTimezone=UTC";
String user = "root";
String password = "88888888";
Connection con = DriverManager.getConnection(url, user, password);
第二步進行語句操做 查詢完關閉sql
//第二步 進行語句操做
Scanner sc = new Scanner(System.in); //能夠輸入sql查詢語句
Statement stm = con.createStatement();
System.out.println("輸入sql語句");
String sql = sc.nextLine();
ResultSet res = stm.executeQuery(sql);
while(res.next()) {//輸出結果集
System.out.println(res.getInt(1)+","+res.getString(2)+","+res.getString(3));
}
if(res!=null)
try {
res.close();
} catch (SQLException e) {
e.printStackTrace();
}
if(pstm !=null)
try {
pstm.close();
} catch (SQLException e) {
e.printStackTrace();
}
if(con !=null)
try {
con.close();
} catch (SQLException e) {
e.printStackTrace();
}
完整代碼數據庫
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.Scanner;
import java.sql.Connection;
public class JDBC {
public static void main(String[] args) {
// 第一步 導入架包 加載驅動程序
// Class.forName("com.mysql.jdbc.Driver");//通常都是已經加載好的
System.out.println("驅動加載成功");
String url = "jdbc:mysql://localhost:3306/mysql2_1709?serverTimezone=UTC";
String user = "root";
String password = "88888888";
Connection con = null;
Statement stm = null;
ResultSet res = null;
try {
con = DriverManager.getConnection(url, user, password);
Scanner sc = new Scanner(System.in);
stm = con.createStatement();
System.out.println("輸入sql語句");
String sql = sc.nextLine();
res = stm.executeQuery(sql);
while (res.next()) {
System.out.println(res.getInt(1) + "," + res.getString(2) + "," + res.getString(3));
}
}
catch (SQLException e) {
e.printStackTrace();
}
finally {// 每一個關閉語句都要單獨 放 否則一個有異常 會致使其餘資源的關閉
if(res!=null)
try {
res.close();
} catch (SQLException e) {
e.printStackTrace();
}
if(pstm !=null)
try {
pstm.close();
} catch (SQLException e) {
e.printStackTrace();
}
if(con !=null)
try {
con.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
// 第二步 進行語句操做
}
}
查詢語句能夠改成apache
System.out.println(res.getInt("id") + "," + res.getString("name") + "," + res.getString("sex"));
整理代碼 把操做寫到方法裏面 查詢數據庫全部信息ide
public static void selectAll() {
Connection con = null;
Statement stm = null;
ResultSet res = null;
try {
con = DriverManager.getConnection(url, user, password);
Scanner sc = new Scanner(System.in);
stm = con.createStatement();
res = stm.executeQuery("select * from t1_user");
while (res.next()) {
System.out.println(res.getInt("id") + "," + res.getString("name") + "," + res.getString("sex"));
}
}
catch (SQLException e) {
e.printStackTrace();
}
// 每一個關閉語句都要單獨 放 否則一個有異常 會致使其餘資源的關閉
finally {
if(res!=null)
try {
res.close();
} catch (SQLException e) {
e.printStackTrace();
}
if(pstm !=null)
try {
pstm.close();
} catch (SQLException e) {
e.printStackTrace();
}
if(con !=null)
try {
con.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
}
經過 指定的id 和name 來查詢 注意 namevalue 要用單引號括起來工具
public static boolean selectByIdName(String id, String name) {// 查詢語句是否存在指定的id 以及 name
Connection con = null;
Statement sta = null;
ResultSet res = null;
try {
con = DriverManager.getConnection(url, user, password);
sta = con.createStatement();
res = sta.executeQuery("select * from t1_user where id= " + id + " and name = '" + name + "'");
// 有數據就返回true 並輸出相對應的信息
if (res.next()) {
while (res.next()) {
System.out.println(res.getInt("id") + "," + res.getString("name"));
}
return true;
}
else
return false;
}
catch (Exception e) {
e.printStackTrace();
}
finally {
if(res!=null)
try {
res.close();
} catch (SQLException e) {
e.printStackTrace();
}
if(pstm !=null)
try {
pstm.close();
} catch (SQLException e) {
e.printStackTrace();
}
if(con !=null)
try {
con.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
return false;
}
}
數據庫要當心sql注入 被黑客攻擊的漏洞 id 和 name 是數據庫裏面沒有的 結果還輸出數據url
防止sql注入 採用 preparedstatement 語句 將上面sql定義的數據改寫爲spa
Connection con = null;
PreparedStatement psta = null;
ResultSet res = null;
try {
con = DriverManager.getConnection(url, user, password);
String sql = "select * from t1_user where id = ? and name = ?";
psta = con.prepareStatement(sql);//建立後再設置參數
psta.setInt(1, id);
psta.setString(2, name);
res = psta.executeQuery();//記得要賦值給 res
分頁查詢
limit 查詢的方法 查詢第幾頁.net
public static void selectUserByPage(int pageNumber , int pageCount) {
Connection con = null;
PreparedStatement pstm =null;
ResultSet res = null;
try {
con = DriverManager.getConnection(url,user,password);
String sql = "select * from t1_user limit ? , ?";
pstm = con.prepareStatement(sql);
pstm.setInt(1, (pageNumber-1)*pageCount);
pstm.setInt(2, pageCount);
res = pstm.executeQuery();
while(res.next()) {
System.out.println(res.getInt(1)+","+res.getString(2)+",");
}
}
catch (Exception e) {
System.out.println(e);
}finally {
if(res!=null)
try {
res.close();
} catch (SQLException e) {
e.printStackTrace();
}
if(pstm !=null)
try {
pstm.close();
} catch (SQLException e) {
e.printStackTrace();
}
if(con !=null)
try {
con.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
}
對代碼進行整合（重複代碼放到一個工具類中） 以及實現一些小功能
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.Scanner;
public class JDBCUtills {
private static final String url = "jdbc:mysql://localhost:3306/mysql2_1709?serverTimezone=UTC";
public static Connection getConn() {
Scanner sc = new Scanner(System.in);
System.out.println("輸入登錄帳號");
String user = sc.nextLine();
System.out.println("輸入密碼");
String password = sc.nextLine();
Connection con = null;
PreparedStatement pstm =null;
ResultSet res = null;
try {
con = DriverManager.getConnection(url,user,password);
System.out.println("登錄成功");
return con;
}
catch (Exception e) {
System.out.println("密碼帳號出錯");
}
return con;
}
public static void close(ResultSet res, PreparedStatement pstm, Connection con) {
if(res!=null)
try {
res.close();
} catch (SQLException e) {
e.printStackTrace();
}
if(pstm !=null)
try {
pstm.close();
} catch (SQLException e) {
e.printStackTrace();
}
if(con != null)
try {
con.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
public static void close(ResultSet res, Statement stm, Connection con) {
if(res!=null)
try {
res.close();
} catch (SQLException e) {
e.printStackTrace();
}
if(stm !=null)
try {
stm.close();
} catch (SQLException e) {
e.printStackTrace();
}
if(con != null)
try {
con.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
}
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.Scanner;
import java.sql.Connection;
public class JDBC {
static String user;
static String password;
static String url;
static Connection con;
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
con = JDBCUtills.getConn();
if (con != null)
selectAll();
}
public static void selectAll() {
Statement stm = null;
ResultSet res = null;
try {
stm = con.createStatement();
res = stm.executeQuery("select * from t1_user");
while (res.next())
System.out.println(res.getInt("id") + "," + res.getString("name") + "," + res.getString("sex"));
}
catch (SQLException e) {
e.printStackTrace();
}
finally {// 每一個關閉語句都要單獨 放 否則一個有異常 會致使其餘資源的關閉
JDBCUtills.close(res, stm, con);
}
}
public static boolean selectByIdName(int id, String name) {// 查詢語句是否存在指定的id 以及 name
PreparedStatement psta = null;
ResultSet res = null;
try {
String sql = "select * from t1_user where id = ? and name = ?";
psta = con.prepareStatement(sql);// 建立後再設置參數
psta.setInt(1, id);
psta.setString(2, name);
res = psta.executeQuery();
// 有數據就返回true 並輸出相對應的信息
if (res.next()) {
while (res.next())
System.out.println(res.getInt("id") + "," + res.getString("name"));
return true;
}
else
return false;
}
catch (Exception e) {
e.printStackTrace();
}
finally {
JDBCUtills.close(res, psta, con);
}
return false;
}
public static void selectUserByPage(int pageNumber, int pageCount) {
PreparedStatement pstm = null;
ResultSet res = null;
try {
String sql = "select * from t1_user limit ? , ?";
pstm = con.prepareStatement(sql);
pstm.setInt(1, (pageNumber - 1) * pageCount);
pstm.setInt(2, pageCount);
res = pstm.executeQuery();
while (res.next()) {
System.out.println(res.getInt(1) + "," + res.getString(2) + ",");
}
} catch (Exception e) {
System.out.println(e);
} finally {
JDBCUtills.close(res, pstm, con);
}
}
}
插入語句的實現代碼
public static void insert(int id , String name , String sex) {
PreparedStatement pstm = null;
ResultSet res = null;
try {
String sql = "insert into t1_user(id,name,sex) values(?,?,?)";
pstm = con.prepareStatement(sql);
pstm.setInt(1, id);
pstm.setString(2, name);
pstm.setString(3, sex);
int n = pstm.executeUpdate();//受影響的行數
System.out.println(n);
}catch(Exception e) {
System.out.println("插入失敗");
}
finally {
JDBCUtills.close(res, pstm, con);;
}
}
更新代碼的實現
public static void update(int id , String name) {
PreparedStatement pstm = null;
ResultSet res = null;
try {
String sql = "update t1_user set name = ? where id = ?";
pstm = con.prepareStatement(sql);
pstm.setString(1, name);
pstm.setInt(2, id);
int n = pstm.executeUpdate();
System.out.println(n);
}catch(Exception e ) {
System.out.println("更新失敗");
}finally {
JDBCUtills.close(res, pstm, con);
}
}
轉帳操做加事務
public static void transferMoney(int id ,int id1, int money) {//兩個以上的操做數據庫 要加上事務
PreparedStatement pstm = null;
PreparedStatement pstm1 = null;
ResultSet res = null;
try {
con.setAutoCommit(false);
String sql = "update t1_user set money = money - ? where id = ?";
pstm = con.prepareStatement(sql);
pstm.setInt(1, money);
pstm.setInt(2, id);
pstm.executeUpdate();
///////////////////////這裏能夠加一段 會報錯的語句 1/0
sql = "update t1_user set money = money + ? where id = ?";
pstm1 = con.prepareStatement(sql);
pstm1.setInt(1, money);
pstm1.setInt(2, id1);
pstm1.executeUpdate();
System.out.println("成功");
con.commit();//提交 若是中間報錯則 回滾數據
}catch(Exception e ) {
System.out.println("轉帳失敗");
}finally {
JDBCUtills.close(res, pstm1, con);
JDBCUtills.close(res, pstm, con);
}
}
將工具類改寫成鏈接池
public class JDBCUtills {
private static ArrayList<Connection> al = new ArrayList<Connection>();
static {
for (int i = 0; i < 5; i++) {
Connection con = createConn();
al.add(con);
}
}
private static final String url = "jdbc:mysql://localhost:3306/mysql2_1709?serverTimezone=UTC";
public static Connection getConn() {
if(!al.isEmpty()) {
Connection con = al.get(0);
al.remove(con);
return con;//通常在用完以後就放回去到鏈接池裏面 就在後面那個關閉Connection 那裏加一個歸還操做
}
else return createConn();
}
private static Connection createConn() {
// TODO Auto-generated method stub
Scanner sc = new Scanner(System.in);
System.out.println("輸入登錄帳號");
String user = sc.nextLine();
System.out.println("輸入密碼");
String password = sc.nextLine();
Connection con = null;
PreparedStatement pstm = null;
ResultSet res = null;
try {
con = DriverManager.getConnection(url, user, password);
System.out.println("登錄成功");
return con;
} catch (Exception e) {
System.out.println("密碼帳號出錯");
}
return con;
}
下面把代碼交給dbcp進行管理 運行的時候出現的錯誤： https://blog.csdn.net/anaini1314/article/details/71157791（mysql版本比較新） https://blog.csdn.net/mqs1990/article/details/76167679（缺乏某些第三方庫）
import java.sql.Connection;
import java.sql.SQLException;
import org.apache.commons.dbcp2.BasicDataSource;
public class dataSource {
private static final String url = "jdbc:mysql://localhost:3306/mysql2_1709?serverTimezone=UTC";
private static final String user = "root";
private static final String password = "88888888";
private static BasicDataSource ds ;
static {
ds = new BasicDataSource();
ds.setDriverClassName("com.mysql.cj.jdbc.Driver");
ds.setUrl(url);
ds.setUsername(user);
ds.setPassword(password);
ds.setInitialSize(5);//初始化鏈接個數
ds.setMaxTotal(20);//達到二十個不會再建立 只有調用close 纔會歸還對象//能夠用以一個for試試
ds.setMinIdle(4);//最小鏈接
}
public static Connection getConnection() {
try {
return ds.getConnection();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return null;
}
}
c3p0 （雖然差很少 但這個用起來不是很方便）
import java.beans.PropertyVetoException;
import java.sql.Connection;
import java.sql.SQLException;
import com.mchange.v2.c3p0.ComboPooledDataSource;
public class c3p0dataSource {
private static final String url = "jdbc:mysql://localhost:3306/mysql2_1709?serverTimezone=UTC";
private static final String user = "root";
private static final String password = "88888888";
private static ComboPooledDataSource cpds ;
static {
cpds = new ComboPooledDataSource ();
try {
cpds.setDriverClass("com.mysql.cj.jdbc.Driver");
cpds.setUser(url);
cpds.setUser(user);
cpds.setPassword(password);
cpds.setInitialPoolSize(5);//初始化鏈接個數
cpds.setMaxPoolSize(20);//達到二十個不會再建立 只有調用close 纔會歸還對象
cpds.setMinPoolSize(4);//最小鏈接
} catch (PropertyVetoException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}public static Connection getConnection() {
try {
return cpds.getConnection();
} catch (SQLException e) {
e.printStackTrace();
}
return null;
}
}